Method of heat setting footwear

ABSTRACT

A method and apparatus for heat setting polymeric components of footwear such as lasted shoe uppers which is characterized in that the material is brought from its hot condition to a handling condition by forced cooling within 1 1/2 minutes; the apparatus comprises an enclosure with radiant heaters and a conveyor so that the articles to be treated are irradiated and subsequently subjected to hot gas trapped in the enclosure and thereafter to forced cooling by water sprays.

a United States Patent 1 91 1111 ,761,562 Skelham Sept. 25, 1973 [5METHOD OF HEAT SETTING FOOTWEAR 3,590,112 6/1971 Civardi 264/3213,558,764 1/1971 Isaacson et al.. 264/346 [75] lnvemor- Walt" ThmnasSkelham, 3,491,177 1/1970 Johnson 264/348 Ketlermg, England 3,551,53612/1970 GUell'CllO 264/346 3,595,836 7/1971 Korneli et al.... 264/235[73] Ass'gnee i 's igfi i gg 'sgg Research 3,577,502 5/1971 Selman etal. 264/346 1 3 7 497 1 Northamptonshirey England 3,57 5/197 Matsugu etal 264/235 [22] Filed: Aug. 5, 1970 Primary Examiner-Donald J. ArnoldAssistant Examiner-Gene Auville [2 App! 6l323 Attorney-Lerner, David &Littenberg [30] Foreign Application Priority Data [57] ABSTRACT Aug. 5,1969 Great Britain 39,113/69 A method and apparatus for heat settingpolymeric components of footwear such as lasted shoe uppers [52] US. Cl.264/346, 264/348 which is characterized in that the material is brought[51] Int. Cl. B29c 25/00 from its hot condition to a handling conditionby forced [58] Field of Search 264/235, 346, 237, cooling within 1%minutes; the apparatus comprises an 264/348, 321 enclosure with radiantheaters and a conveyor so that the articles to be treated are irradiatedand subse- [56] References Cited quently subjected to hot gas trapped inthe enclosure wq STATES PATENTS and thereafter to forced cooling bywater sprays.

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METHOD OF HEAT SETTING FOOTWEAR This invention relates to shoe-makingand in particular to the employment in shoe-making of the recentlydeveloped so-called poromeric materials. These poromeric materials, suchas are now widely available under the trade name CORFAM, HITELAC,"OR'llX, CLARINO," PORVAIR, are porous, leather-like, synthetic sheetmaterials comprising a microporous layer of a polyurethane or similarpolymeric material. Some materials comprise a non-woven fibrous baselayer bonded to the microporous layer and some a further woven fabricinterlayer between the microporous and base layers; in such compositematerials the bonding agent for the layers is usually polyurethane, orsimilar polymer, derived from the microporous layer. The microporouslayer itself normally comprises at least two zones, analogous to anatural leather, namely an inner zone and an'outer grain or finish zone.The poromeric materials are coming increasingly into use in shoe-making,in particular as replacement for leather and other plastics materials inshoe uppers.

While the present invention is generally applicable to all currentlyavailable poromeric shoe upper materials, it is particularly suitablefor the treatment of that material currently sold under the RegisteredTrade Mark PORVAIR," which is an elastomeric, thermoplastic, microporoussheet material free from fibrous reinforcement. It is normally dyed orpigmented at least over one surface.

DESCRIPTION OF THE PRIOR ART It is well known that even after lasting,the uppers of leather shoes will tend to deform as a result of thenatural resilience of the material and its resistance to the shapingtreatments and in particular the stretching which takes place duringlasting. For this reason shoes are given a setting treatment and themost suitable treatment available is what is called moist heat setting.This consists of subjecting the lasted shoe to a cyclic treatment whichmay consist for example of steaming for 1% minutes at 65C followed byblasting with hot air at 120C.

Poromeric materials have an even greater tendency to recovery of theearlier shapes than leather. These materials are normally based uponpolyurethane in which there is substantial hydrogen bonding present.Thus flexible polyurethanes and similar materials such as polyester andpolyester amides which have similar hydrogen bonding in the structurebetween the polymeric chains or three-dimensional molecules do notexhibit good shape retention and the heat setting treatments availablefor leather uppers do not in practice produce a good response inporomeric materials.

Polyurethanes are derived from the reaction of polyisocyanates withmaterials such as polyols containing reactive hydrogen atoms, the NCOgroups of the isocyanates being converted into -NHCO linkages whichprovide the propensity to hydrogen bonding. During the lasting orforming processes, molecular rearrangement occurs and it is though thatthis in turn produces stresses in the hydrogen bonds existing in thematerial as well as in other intro or inter-molecular atomic andmolecular forces present in the structure.

I have proposed in an earlier dated British Patent Application a methodof heat setting a shaped article of a poromeric material which comprisessubjecting the article to dielectric heating followed by cooling, whilethe material is maintained in the desired shape.

While very successful results may be obtained through dielectric heatingas described in the said specification, the method involves the use ofexpensive dielectric heating apparatus, especially where whole shoes areto be subjected to the treatment, where complex electrodes are required.The present invention provides a process more suited to the massproduction of shoes. One of the difficulties associated with the heatsetting of poromeric materials is that they require to be heated to atemperature e.g. approaching the critical temperature of the material.At this stage they are not only too hot to handle, but are very easilydamaged and marked by contact with the hands or other surfaces, and suchmarks cannot afterwards be made good". Furthermore, still the heatsetting process is akin to an annealing treament, it has always beenfelt that slow cooling of the material is necessary. This greatlyincreases the time cycle of the heat setting treatment and consequentlythe cost of manufacture as well as the risk of damage. We have now foundthat these disadvantages can be overcome by introducing a quick forcedcooling step at the end of the heat treatment.

SUMMARY OF THE INVENTION The invention is aimed at overcoming the abovedisadvantages and providing stress relaxation in poromeric materials bya heat treatment which is designed to produce as far as possible uniformheating throughout the material thereby minimising the likelihood ofdamage to the surface material which would tend to be produced byexternal forms of heat application. The treatment is aimed at breakingdown the stressed hydrogen bonds so that upon cooling fresh bonds willform in unstressed positions.

According to the invention there is provided a method of heat settingshaped poromeric components of footwear characterised in thatimmediately after heat treatment and while the components are still at atemperature of C or more and while they continue to be maintained in thedesired shape, they are subjected to forced cooling sufficient to bringthem to a handling temperature within a period not exceeding 1% minutes.

The method not only results in adequate heat setting in safety and withreduced cost but unexpected improvements in results have been obtained.

The process allows and preferably involves the use of radiant heat inraising the temperature of the shoe upper material. Radiant heat usedalone has never been a satisfactory form of heating for use with leatheror artificial leather materials due to the very high temperaturegradient produced between the exposed and shadow surfaces of thematerial. Thus unless the intensity of radiation is reduced to a minimumand the process carried out over an inordinately long period, scorchingof the exposed surface or melting, in the case of thermoplasticmaterials, tends to take place. The preferred method of the presentinvention involves a cycle of different heating steps followed by acooling step which can be carried out in relatively cheap apparatus withsurprisingly good results.

Thus the preferred method comprises subjecting the article successivelyto radiant heat, a hot gas atmosphere, and forced cooling, while thematerial is maintained in the desired shape.

The process produces a rapid heating of the outer layers of the materialfollowed by a period in which the heat is distributed more uniformlythroughout the thickness of the material.

The combination of radiant and conductive heating steps employed in thisprocess enables the temperature to be raised throughout the body of theporomeric material to the necessary level, in sufficiently rapid timefor a commercially desirable process, notwithstanding the difficultycaused by the cellular-like structure of the poromeric. This difficultyis of course particularly acute with poromeric materials consisting ofthe microcellular layer only.

However the heat treatment may be conducted in any suitable manner, forexample, simply by using a hot gaseous atmosphere or by impingement ofthe components with a stream of hot gas, if necessary followed byfurther heating in a still atmosphere of hot gas.

Forced cooling is preferably achieved by directing a spray of coldliquid, in particular water, against the poromeric material, thelatent'heat of evaporation for the liquid droplets being supplied inpart at least by the poromeric material and hence accelerating itscooling. Surprisingly the resulting shoe or upper is hardly if at allwet. Alternatively, a stream of cold gaseous fluid, in particular air,can be directed against the poromeric material for example by means of afan, and this procedure may be advantageous in certain circumstances.

Preferably the heat treatment is of sufficient intensity and duration tobring the surface temperature of the poromeric material to a temperatureapproaching but not substantially exceeding the critical temperature (asdefined herein) of the poromeric material.

The hot gas, when it follows radiant heating is preferably at atemperature less than the critical temperature (as defined herein) ofthe poromeric material.

In general it may be said that the surface temperature of the articleshould preferably be raised e.g., under the radiant heating to an upperlimit not exceeding 160C and more preferably from 130C to 160C. Asuitable temperature range for subsequent treatment with hot gas is 80Cto 150C, the optimum temperature being about 100C, e.g., 90C to 110C.

The force cooling is preferably carried out with a stream of air andwater spray having a velocity of at least feet per second, 5 to feet persecond being a useful range of velocities.

In the preferred process the article to be treated is carried insuccession past a plurality of radiant heat sources, through anenclosure containing hot air and past a jet emitting a spray of cold airand water..

Preferably the air in the enclosure is heated by the radiant heatsources, but it could be heated by any other effective means such asadditional radiant heaters or an external hot gas generator.

The article is preferably subjected to radiant heating for 3 to 4minutes, to hot gas for 3 to 5 minutes and to forced cooling for /4 to1% minutes, the total treatment preferably not exceeding 8 minutes.

An apparatus is disclosed for the heat setting of lasted articles offootwear having uppers or upper components of poromeric materialcomprising a conveyor arranged to receive the said lasted articles, andto convey them in succession past a heat treatment zone comprising meansfor heating the poromeric material to a heat setting temperature andthereafter, while they are still at a temperature of 100C or more, pasta forced cooling zone comprising means for subjecting the articles toforced cooling sufficient to bring them to a handling temperature withina period not exceeding 1% minutes.

Preferably the conveyor is arranged to receive the said lasted articles,and to convey them in succession past first, second and third treatmentzones,

a first treatment zone comprising a plurality of radiant heat emittersarranged in succession at spaced positions from one another and from theconveyor so that collectively they will bring all portions of the uppersof the articles to a uniform temperature not substantially exceeding thecritical temperature of the poromeric material,

a second treatment zone comprising an enclosure through which theconveyor passes, means being provided for heating the air in theenclosure to a temperature less than the said critical temperature, and

a third treatment zone comprising means for force cooling the saidarticles to a handling temperature.

The preferred apparatus comprises an enclosure, a said conveyor runningin a vertical closed loop in said enclosure, the said radiant heatemitters being arranged within the lower part of the enclosure, theupper part of the enclosure forming a hot air trap, an access opening inthe enclosure between the first emitter and the hot air trap and anair/water spray nozzle arranged to direct a cooling spray into saidenclosure above said access opening.

The emitters conveniently comprise rod elements which extendhorizontally and transversely to the plane of the conveyor loop. Theemitters adjacent the floor of the enclosure are preferably of higherpower than those higher up and adjacent the walls. The minimum distanceof the radiant heat emitters, which may be of 1 to 2 KW each shouldpreferably be from 3% to 6 inches.

An extractor fan is preferably fitted to said hot air trap and operatedin dependence upon a thermostat to maintain the hot air temperaturewithin predetermined limits.

Preferably a plurality of spray nozzles are arranged to direct a sprayat a pressure of 5 to 10 lbs/sq.in., an air flow of 1% to 4 cubicfeet/min. and water flow of A to 4 pints/hour per nozzle towards thearticles.

The preferred process and an embodiment of apparatus in accordance withthe invention are hereafter more particularly described with referenceto the accompanying drawings in which:

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagrammatic side elevationalview of a suitable skeleton apparatus illustrating the process cycle,

FIG. 2 is a front elevational view of the apparatus,

FIG. 3 is a sectional view along the line III-III of FIG. 2,

FIG. 4 is an enlarged view of a portion of FIG. 2,

FIG. 5 is a top plan view of a lasted shoe for fitment to the conveyorof the apparatus, and

FIG. 6 is a time-temperature graph showing the temperatures to whichvarious parts ofa shoe are subjected during the process cycle.

DETAILED DESCRIPTION OF DRAWINGS Turning to FIG. 1 there is shown asuitable skeleton apparatus for carrying out the process cycle. Thisconsists of an enclosure 1 having an opening 2 through which a shoe orother article to be treated can be fitted by a continuous chain conveyor3. Radiant heatemitters 4 are arranged in a horseshoe around the lowerpart of the enclosure and provided with reflectors 5 which direct theradiant heat upwardly and towards the conveyor 3. The part of theenclosure above the opening 2 forms a trap for hot air. The shoe isfitted to the conveyor 3 through the opening 2 and travels downwardly inthe direction of the arrow 6 past the radiant heaters so that variousparts of the shoe are successively turned more directly towards theheaters 4. The shoe is normally in the inverted position so that theheaters at the bottom radiate over the top of the upper. A partition 8is positioned centrally between the runs of the conveyor. As shown bythe arrow at the right hand side of the drawing, the radiant heattreatment takes about 3 minutes after which the shoe passes upwardly andthen downwardly through the hot air trap to the position of the forcedcooling unit indicated at 7, which takes 7% minutes. The cooling maytake 1% minute to bring the shoe in front of the opening 2 for thesecond time whereupon it is removed.

FIGS. 2 to 4 show the apparatus in more detail. In,

this apparatus the enclosure 1 can be considered as divided into twoidentical halves served respectively by opposite sides of the centrallysituated conveyor 3. Each enclosure half has an opening 2,2', theopenings being separated by a glass window 9. The hot air trap at thetop of the enclosure 1 is provided with an extractor fan 10 connected incircuit with a thermostat (not shown) to maintain the hot airtemperature in the upper part of the enclosure 1 to the desired temperature, normally 100C.

The radiant heating elements 4, 4' extend across the full width of theenclosure and are shown in greater detail in FIG. 3.

As shown in FIG. 3 the walls of the enclosure 1 are formed of steelsheets 11 lined with insulating material such as asbestos cladding 12.Each heating unit consists of one or more elements 4 supported by endsupports 13 pivotally mounted to brackets 14 fitted to the walls orfloor. The walls or floor are shielded from the elements by a reflector5.

The conveyor chain 3 is composed of links 15 and a shoe support 16, oneof which appears in FIG. 4, is attached to every third link axle on eachside of the conveyor, so as to pivot therefrom. The shoe support 16comprises a right-angled bracket 17, one limb of which projectsoutwardly from the chain as shown in FIG. 4 and has fastened to it aconnecting means consisting of an upright pin 18 adapted to fit in acorresponding bore 40 (FIG. 5) in the ankle portion ofa last, and asupporting seat member 19 against which the upper sides 41 (FIG. 5) ofthe ankle portion of the last rest when the last is inverted and fixedin place on the support 16. Since the shoe supports 16 pivot as shownespecially in FIG. 3, the shoe is always in the inverted position. InFIG. 3 the chain-dotted lines 20 and 21 indicate respectively thepositions of the inside edge and outside edge of a size 7 shoe fitted tothe support. The dimensions a, b and c indicate the distances of variousradiant heating elements from the adjacent surface of the shoe, thedimension a being for example 5% inches, b being for example 4% inchesand 0 being 4 5/16 inches.

The conveyor chain 3 is mounted to a respective upper pulley wheel 22and lower pulley wheel 23, the wheel 23 being shown in FIG. 3. The upperpulley wheel 22 is mounted to an axle 24 which extends the whole widthof the enclosure 1 and rotates in bearings 25, 25'. The lower pulleywheel 23 is mounted on an axle 26 which rotates on bearings 27, 27'. Thepartition 8 may be for example of sheet steel. The axle 26 is attachedto a pulley wheel 29 connected by a belt or chain to a second pulleywheel 30 connected to a motor 31 via a reduction gear unit 32 so thatthe axle 26 rotates at the appropriate slow speed.

Spray nozzles 34 project through the sides of the enclosure 1 in thevicinity of each window or opening 2, 2' so as to cool a shoe after itreaches the end of the hot air treatment and approaches the opening. Thenozzles may be of the type sold as Watford Setup G83 and available fromThe Aerospray Association. These nozzles form a part ofa spray gun unitoperating at the low air pressure of 7% lbs per square inch and producea very fine mist spray which is easily controlled. The nozzles arepositioned to cool the maximum area of the upper face. In operation verylittle liquid moisture is formed on the uppers when the guns arecorrectly adjusted. Three nozzles are used adjacent each opening 2,arranged in an inverted triangle in two horizontal rows as shownparticularly in FIG. 4. The upper nozzles are positioned about sixinches apart on the front or window side of the partition 8. The lowercentral nozzle is about 8 inches below the others and the nozzles areabout 16 inches from the support pin 18 (FIG. 4). They have a totalspray angle of 60. Each nozzle has separate adjustment valve 35 and acentral pressure control 36 is provided for the whole water circuit.

FIG. 6 shows the temperature of the various parts of the size 7 shoewhich has passed through the apparatus, the various lines referring tothe toe, the tab at the heel of the shoe, the stiffener (between theouter and lining at the heel), the cone, the lasted margin and the backseam. The various temperatures were obtained with thermocouples.

The temperature curves clearly indicate the problems involved when anirregular surface is heated by radiant heat. Some parts of the shoe arehotter than others. The highest temperature recorded is 134C at the tabpoint, closely followed by the temperature at the stiffener. Atemperature of only 78C was recorded in the lasting cement and mostcommercial lasting cements will easily withstand this temperature. Thehighest temperature recorded is well below the damage point or criticaltemperature of most poromeric materials but the thermocouples werepositioned below the surface and actual surface temperatures werehigher. Furthermore, larger sized shoes will obviously approach theradiant heaters more closely so that higher temperatures may beexpected. Clelsea boots manufactured from Porvair material have beensuccessfully treated by the apparatus described in the drawings.

After 8 minutes heating all parts of the upper were in the temperaturerange C to C, thus making the shoe too hot to handle and liable todamage by touching. The water spray rapidly reduced the temperature; atthe toe for example the temperature was brought down to 50C and otherparts were brought down to about 70C. In practice the shoes werecomfortable to handle.

TABLE 1 Percentage set after one week Material Standard Moist SatraRadiant Heat Setting Heat Setting Xylee 50 69 Corfam 61 81 Ortix 38 55Hi-Telac 72 34 Patora 42 69 Porvair 40 (,4

Clarino 49 61 The results of further experiments are given in Table 2below. In these experiments the heat-setting was tested after variousperiods; the initial period refers to shoes immediately removed from thelast. The Table shows the importance of using one week percentage setfigures. Very high initial percentage set figures can be obtained on allthe poromeric materials tried but considerable recovery takes placeafter one week. The sets are, however, much higher than can be obtainedusing normal moist-heat setting conditions. Furthermore the DomePlasticity Apparatus used introduces cooling effects so that even thelowest set appearing in the Table provides an acceptable level forshoe-making.

TABLE 2 Percentage set Material lnitial 1 hour 24 hours 1 week Xylee92.5 79.3 73.1 64.0 Corfam 92.0 85.4 82.9 79.8 Ortix 85.5 74.6 62.1 54.0Hi-Telac 94.1 91.3 88.8 80.2 Patora 90.7 82.0 73.3 65.8 P rva r 81.274.9 70.4 64.6 Clam") 85.5 73.2 66.6 57.0

While the poromeric material is preferably maintained in shape on a shoelast, it may be maintained in shape by means of a female mould derivedfrom a shoe last, a part shoe last, a part female mould derived from ashoe last, and a male or female mould affording a moulding surface asclaimed or described in Belgian Patent 745132.

What 1 claim is:

l. A method of heat setting shaped components of footwear composed ofpolyurethane-based poromeric shoe upper material in which saidcomponents are subjected to a continuous treatment cycle comprising:

a. subjecting the shoe upper material to a radiant heat treatment inwhich the components are brought to a maximum temperature of C to 160Cin 3 to 4 minutes,

b. then subjecting the so-heated shoe upper material to a second heattreatment in which heating of the components is continued in a hot gasatmosphere at 80C-to C for 3 to 5 minutes, and

c. forced cooling by subjection to a coolant fluid selected from thegroup consisting of air and water spray, for up to 1 h minutes.

2. A method as claimed in claim 1 wherein the forced cooling is cariedout with a stream of air and water spray having a velocity of at least 5ft./sec.

3. A method as claimed in claim 1 wherein the total heating and coolingcycle does not exceed 8 minutes.

4. A method as claimed in claim 1 wherein the heat treatment is ofsufficient intensity and duration to bring the surface temperature ofthe poromeric material to a temperature approaching but notsubstantially exceeding the critical temperature of the poromericmaterial and wherein the hot gas is at a temperature less than thecritical temperature of the poromeric material.

5. A method as claimed in claim 1 wherein the article is subjected toradiant heating for 3% minutes, to hot air for 4 minutes and to forcedair cooling for one-half minute.

6. A method as claimed in claim 1 wherein the components are carried insuccession past a plurality of radiant heat sources, through anenclosure containing hot air and past ajet emitting a spray of cold airand water.

7. A method as claimed in claim 6 wherein the air in the enclosure isheated by the radiant heat sources.

2. A method as claimed in claim 1 wherein the forced cooling is carriedout with a stream of air and water spray having a velocity of at least 5ft./sec.
 3. A method as claimed in claim 1 wherein the total heating andcooling cycle does not exceed 8 minutes.
 4. A method as claimed in claim1 wherein the heat treatment is of sufficient intensity and duration tobring the surface temperature of the poromeric material to a temperatureapproaching but not substantially exceeding the critical temperature ofthe poromeric material and wherein the hot gas is at a temperature lessthan the critical temperature of the poromeric material.
 5. A method asclaimed in claim 1 wherein the article is subjected to radiant heatingfor 3 1/2 minutes, to hot air for 4 minutes and to forced air coolingfor one-half minute.
 6. A method as claimed in claim 1 wherein thecomponents are carried in succession past a plurality of radiant heatsources, through an enclosure containing hot air and past a jet emittinga spray of cold air and water.
 7. A method as claimed in claim 6 whereinthe air in the enclosure is heated by the radiant heat sources.